Fluororesin aqueous dispersions are usually produced by emulsion polymerizing a fluoromonomer in the presence of a fluorosurfactant. The fluorosurfactant conventionally used is a long-chain fluorosurfactant such as perfluorooctanoic acid or a salt thereof.
Patent Literature 1 discloses that ammonium perfluorooctanoate is a substance which does not exist in the nature and is difficult to decompose, so that restraint of exhaustion thereof is proposed from the viewpoint of environmental preservation, and also discloses that this substance is highly bioaccumulative.
Patent Literature 1 proposes a polytetrafluoroethylene aqueous emulsion obtained by emulsion polymerizing tetrafluoroethylene alone or with a monomer copolymerizable therewith in an aqueous medium using a fluorine-containing emulsifier represented by the formula:XCF2CF2(O)mCF2CF2OCF2COOA(wherein X is a hydrogen atom or a fluorine atom; A is a hydrogen atom, an alkali metal, or NH4; and m is an integer of 0 or 1) in an amount of 1,500 to 20,000 ppm relative to the final polytetrafluoroethylene yield.
Patent Literature 2 discloses a low molecular weight polytetrafluoroethylene aqueous dispersion produced by a method for producing a low molecular weight polytetrafluoroethylene. The method includes emulsion polymerizing tetrafluoroethylene alone or tetrafluoroethylene and a modifying monomer copolymerizable with the tetrafluoroethylene in an aqueous medium in the presence of a reactive compound and a chain-transfer agent, wherein the reactive compound has a hydrophilic group and a functional group reactive in radical polymerization, and is used in an amount corresponding to more than 10 ppm relative to the aqueous medium.
Patent Literature 3 discloses an aqueous dispersion of fluoropolymer particles produced by a method for producing an aqueous dispersion of fluoropolymer particles. The method includes the steps of: preparing dispersed particles of a fluorinated ionomer in an aqueous polymerization medium; and polymerizing at least one fluorinated monomer in the presence of the dispersed particles of the fluorinated ionomer and an initiator in the aqueous polymerization medium to form an aqueous dispersion of fluoropolymer particles.